+/**
+ * SECTION:option
+ * @Short_description: parses commandline options
+ * @Title: Commandline option parser
+ *
+ * The GOption commandline parser is intended to be a simpler replacement
+ * for the popt library. It supports short and long commandline options,
+ * as shown in the following example:
+ *
+ * `testtreemodel -r 1 --max-size 20 --rand --display=:1.0 -vb -- file1 file2`
+ *
+ * The example demonstrates a number of features of the GOption
+ * commandline parser:
+ *
+ * - Options can be single letters, prefixed by a single dash.
+ *
+ * - Multiple short options can be grouped behind a single dash.
+ *
+ * - Long options are prefixed by two consecutive dashes.
+ *
+ * - Options can have an extra argument, which can be a number, a string or
+ * a filename. For long options, the extra argument can be appended with
+ * an equals sign after the option name, which is useful if the extra
+ * argument starts with a dash, which would otherwise cause it to be
+ * interpreted as another option.
+ *
+ * - Non-option arguments are returned to the application as rest arguments.
+ *
+ * - An argument consisting solely of two dashes turns off further parsing,
+ * any remaining arguments (even those starting with a dash) are returned
+ * to the application as rest arguments.
+ *
+ * Another important feature of GOption is that it can automatically
+ * generate nicely formatted help output. Unless it is explicitly turned
+ * off with g_option_context_set_help_enabled(), GOption will recognize
+ * the `--help`, `-?`, `--help-all` and `--help-groupname` options
+ * (where `groupname` is the name of a #GOptionGroup) and write a text
+ * similar to the one shown in the following example to stdout.
+ *
+ * |[
+ * Usage:
+ * testtreemodel [OPTION...] - test tree model performance
+ *
+ * Help Options:
+ * -h, --help Show help options
+ * --help-all Show all help options
+ * --help-gtk Show GTK+ Options
+ *
+ * Application Options:
+ * -r, --repeats=N Average over N repetitions
+ * -m, --max-size=M Test up to 2^M items
+ * --display=DISPLAY X display to use
+ * -v, --verbose Be verbose
+ * -b, --beep Beep when done
+ * --rand Randomize the data
+ * ]|
+ *
+ * GOption groups options in #GOptionGroups, which makes it easy to
+ * incorporate options from multiple sources. The intended use for this is
+ * to let applications collect option groups from the libraries it uses,
+ * add them to their #GOptionContext, and parse all options by a single call
+ * to g_option_context_parse(). See gtk_get_option_group() for an example.
+ *
+ * If an option is declared to be of type string or filename, GOption takes
+ * care of converting it to the right encoding; strings are returned in
+ * UTF-8, filenames are returned in the GLib filename encoding. Note that
+ * this only works if setlocale() has been called before
+ * g_option_context_parse().
+ *
+ * Here is a complete example of setting up GOption to parse the example
+ * commandline above and produce the example help output.
+ * |[<!-- language="C" -->
+ * static gint repeats = 2;
+ * static gint max_size = 8;
+ * static gboolean verbose = FALSE;
+ * static gboolean beep = FALSE;
+ * static gboolean randomize = FALSE;
+ *
+ * static GOptionEntry entries[] =
+ * {
+ * { "repeats", 'r', 0, G_OPTION_ARG_INT, &repeats, "Average over N repetitions", "N" },
+ * { "max-size", 'm', 0, G_OPTION_ARG_INT, &max_size, "Test up to 2^M items", "M" },
+ * { "verbose", 'v', 0, G_OPTION_ARG_NONE, &verbose, "Be verbose", NULL },
+ * { "beep", 'b', 0, G_OPTION_ARG_NONE, &beep, "Beep when done", NULL },
+ * { "rand", 0, 0, G_OPTION_ARG_NONE, &randomize, "Randomize the data", NULL },
+ * { NULL }
+ * };
+ *
+ * int
+ * main (int argc, char *argv[])
+ * {
+ * GError *error = NULL;
+ * GOptionContext *context;
+ *
+ * context = g_option_context_new ("- test tree model performance");
+ * g_option_context_add_main_entries (context, entries, GETTEXT_PACKAGE);
+ * g_option_context_add_group (context, gtk_get_option_group (TRUE));
+ * if (!g_option_context_parse (context, &argc, &argv, &error))
+ * {
+ * g_print ("option parsing failed: %s\n", error->message);
+ * exit (1);
+ * }
+ *
+ * ...
+ *
+ * }
+ * ]|
+ *
+ * On UNIX systems, the argv that is passed to main() has no particular
+ * encoding, even to the extent that different parts of it may have
+ * different encodings. In general, normal arguments and flags will be
+ * in the current locale and filenames should be considered to be opaque
+ * byte strings. Proper use of %G_OPTION_ARG_FILENAME vs
+ * %G_OPTION_ARG_STRING is therefore important.
+ *
+ * Note that on Windows, filenames do have an encoding, but using
+ * #GOptionContext with the argv as passed to main() will result in a
+ * program that can only accept commandline arguments with characters
+ * from the system codepage. This can cause problems when attempting to
+ * deal with filenames containing Unicode characters that fall outside
+ * of the codepage.
+ *
+ * A solution to this is to use g_win32_get_command_line() and
+ * g_option_context_parse_strv() which will properly handle full Unicode
+ * filenames. If you are using #GApplication, this is done
+ * automatically for you.
+ *
+ * The following example shows how you can use #GOptionContext directly
+ * in order to correctly deal with Unicode filenames on Windows:
+ *
+ * |[<!-- language="C" -->
+ * int
+ * main (int argc, char **argv)
+ * {
+ * GError *error = NULL;
+ * GOptionContext *context;
+ * gchar **args;
+ *
+ * #ifdef G_OS_WIN32
+ * args = g_win32_get_command_line ();
+ * #else
+ * args = g_strdupv (argv);
+ * #endif
+ *
+ * // set up context
+ *
+ * if (!g_option_context_parse_strv (context, &args, &error))
+ * {
+ * // error happened
+ * }
+ *
+ * ...
+ *
+ * g_strfreev (args);
+ *
+ * ...
+ * }
+ * ]|
+ */